Pinocytotic function of the membrane vesicles, or caveolae, in heart muscle cells

The structure of membrane vesicles present in the sinus node, the atrium, and the ventricular cells of rabbits and mice was investigated. The results described in this study support the idea that membrane vesicles are not pinocytotic vesicles, but structural components of the membrane that increase the sarcolemmal surface area. That is the reason why we prefer to call them caveolae. Why these caveolae are much more abundant in sinus node cells and in Purkinje fibers, as shown by Mobley and Page (1972), than in working myocardium is still unknown.